Hydrostatic thrust bearing

ABSTRACT

A hydrostatic thrust bearing for supporting a load member on a support member is disclosed wherein pressurized fluid is admitted into a cavity formed between opposed surfaces of the load and support members. Lands integral with the load and support members form an annular leakage path through which the pressurized fluid is permitted to escape from the cavity, at least one annular disc being disposed between the lands thereby dividing the leakage path into at least two parallel passages.

United States Patent 1191 Kraus Jan. 29, 1974 [54] HYDROSTATIC THRUSTBEARING 3,619,016 11/1971 Kraus 308/160 Inventor: Charles E. s, us n Tex1,096,174 10/1911 Anker-Holth 308/172 [73] Assignee: Excelermatic, lnc.,Rochester, N.Y. Primary ExaminerChar1es J. Myhre Filed y 23 1972Assistant Examiner--R. H. Lazarus [2]] Appl. No.: 256,143 [57] ABSTRACTI A hydrostatic thrust bearing for supporting a load 52 us. CI 308/160,308/9, 308/172 member on a pp member is disclosed wherein 51] 1111.01.Fl6c 1/24 Pressurized fluid is a\dmitted into a cavity formed 58 Field61 Search 308/160, DIG. 4, 170, 171, tween Opposed surfaces the load andSupport 308/172, 164, 122, 9, 174, 175, 176 bets. Lands integral withthe load and support members form an annular leakage path through whichthe [5 References Cited pressurized fluid is permitted to escape fromthe cav- UNIT ity, at least one annular disc being disposed between 3382014 E T PATENTS 308/9 the lands thereby dividing the leakage pathinto at ar ey 3,635,534 8/1969 Barnett... 308/160 least two Parallelpassages 3,495,886 2/1970 Roberts 308/160 18 Claims, 9 Drawing FiguresL2. 83 e4 82 as 'Z /r/ 31:31: T P

PAIENTEnJms m4 $788,713

SHEET 1 [IF 3 FIG.!

means SHEU 2 OF 3 PATENTEDJAN 29 I974 IIII IIIIII HYDROSTATIC THRUSTBEARING BACKGROUND OF THE INVENTION In hydrostatic thrust bearings apressurized fluid is introduced in a space formed between opposed surfaces of a load member and a support member. The pressurized fluid isadmitted to that space at a predetermined rate and permitted to escapethrough a path formed betwen opposite lands integral with the supportand the load members thereby separating the support and load membersfrom each other.

Such an arrangement is, for example, shown in this inventors earlierU.S. Pat. No. 3,619,016, wherein pressurized fluid is admitted to acentral cavity and escapes therefrom through a path formed between widelands.

The energy required to operate such thrust bearings comprises the powernecessary to drive a pump for the 'supply of the pressurized fluid andthe energy consumed to overcome the shearing forces in the fluid betweenthe support and load members. Most of the shearing losses occur in thefluid between the lands because of the small gap anda large differencein speed between the lands. The greater the gap between the lands, thesmaller, of course; are the shear losses. The size of the gap, however,is limited by the load of the load member and the volume of pressurizedfluid supplied to the bearing.

The losses due to shear in the fluid film in the land area are a squarefunction of the difference in speed between the opposite land surfacesand if the fluid used has a high viscosity the losses caused by theshear are so high that the practical speed permitted by the bearing isquite limited.

SUMMARY OF THE INVENTION The present invention provides a hydrostaticthrust bearing in which a pressurized fluid is admitted to a cavitybetween matching surfaces of a loadmember and a support member so thatthe load member is supported on the support member by the pressurizedfluid. The support and load members have oppositely disposed landsforming a gap through which the fluid escapes and at least one annulardisc is disposed between the lands to divide the fluid path between thelands into at least two parallel passages.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows schematically a thrustbearing according to the invention;

FIG. 2 shows the land area of the bearing with a number of discsdisposed between the lands, and

FIGS. 3 to 9 show arrangements of various discs disposed between thelands.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. I shows schematically thearrangement according to the invention wherein a load member 1 issupported on a support member 2 by a hydrostatic bearing structure.Between the load and the support members 1 and 2 there is formed acavity 3 to which pressurized fluid is admitted through a pressurizedfluid passage 4. The pressurized fluid supports the load member 1 and ispermitted to escape from the cavity'3 through annular passages definedbetween opposite land surfaces 6 and 5 formed on the load and supportmembers 1 and 2. One or more annular discs 7 are disposed between thelands 5 and 6 thereby to form a number of parallel passages 8 (FIG. 2)between the discs 7 and adjacent the land surfaces 5 and 6.

As shown in FIG. 1, the lands and the annular discs are curved such thatthe annular passages between the lands, while having substantiallyradially extending inlet areas, have outlet areas which are inclined inone direction with respect to the axis of the load member. The discsdisposed between the lands are curved accordingly and are essentiallydish-shaped. However, the inclined area may also be provided at theinlet end of the fluid passages 8. Such arrangements center the bearingportions of the load and support members relative to each other becauseradial fluid pressure forces occur in the inclined portions of thepassages. Furthermore, with discs of uniform thickness, the spacingbetween the discs is smallest where the inclination of the passages islargest such that, in the arrangement of FIG. 1, for example, passages 8of decreasing width are formed between discs of uniform thickness asmore clearly shown in FIG. 2. v

In the example shown in FIG. 2, five annular discs 7 of uniformthickness are disposed between the lands 5 and 6. As can be readilyseen, the distance d1 between the lands is larger at the entrance end ofthe fluid path than the distance d2 at the exit end of the fluid path sothat gaps 81 are formed between the annular discs 7 at the entrance endof the fluid path. The discs 7, when not separated from each other bypressurized fluid, contact each other in the area of their greatestinclination with respect to a plane normal to the axis of the bearingstructure which, in the arrangement shown in FIG. 2, is at the exit endof the fluid path.

If there is a relatively large inclination of the land surfaces and thediscs near the exit end of the fluid passage, the gaps 81 are relativelylarge permitting the pressurized fluid to maintain between the discs 7and adjacent the lands 5 and 6 a relatively large pressure which dropssharply only at the radially outer ends of the discs 7, where arelatively small gap 82 is formed. This may cause occasional contactbetween the rings at their outer edges.

Therefore, in one embodiment 'of the invention as shown in FIG. 3, thethickness of the discs 7 is reduced at their radially outer end wherethe thickness is only h2 as compared to hl at the inner end such thatcontact between the discs may occur only at an area C somewhat removedfrom the exit end of the flow path. This arrangement substantiallyreduces the probability of contact occurring between adjacent surfacesbecause of pressure build-up in the smallest width area of the fluidpassages between the discs 7.

FIG. 4 shows an embodiment of the invention in which rings of differentcurvature 7a and 7b are alternately disposed between the land surfaces 5and 6 so that two adjacent rings 7a and 7b engage each other at theirradially inner and outer ends and, together, form a composite annulardisc 7. Adjacent composite discs 7 form therebetween passages which havetheir smallest width at D from which area the width of the passagesincreases toward the radially inner and outer ends 81 and 82 of theleakage paths. As shown in FIG. 4 the rings 7a have a larger radius ofcurvature than the rings 7b so that between each ring 7a and theadjacent ring 7b disposed, at the, with respect to the center ofcurvature, inner side of the ring 7a, a fluid flow passage 8 is formed.The ring 7b, disposed at the, with respect to the center of curvature,outer side of ring 7a engages the ring 7a at the fluid inlet and outletends so that no fluid flow path is formed therebetween.

In such an arrangement, the rings forming a composite disc are exposedto different pressures on opposite sides and yield somewhat such thatthe divergence rate of the fluid flow passages will decrease when thefluid pressure increases. However, the rings can be made stiff enough tomaintain operative divergence rates at rated pressures.

This arrangement takes more bearing space than the arrangement shown inFIG. 3 but it provides for a resilient bearing structure whichaccommodates considerable vibration, out-of-line running or wobble ofthe load member.

' FIG. 5 shows an arrangement wherein the fluid path between lands 5 and6 and the discs 7 disposed in the fluid path are dish-shaped formingtherebetween passages 8 with essentially radial inlet areas 81 andoutlet areas 82, the intermediate area being inclined in one directionwith respect to the axis of the load member 1 and the support member 2.

Such an arrangement provides fluid passages 8 along the discs 7 whichare wider in the inlet and outlet areas 81 and 82 than in theintermediate area with the discs 7 being of uniform thickness.

As shown in FIGS. 6 t0 9, the discs 7 may also be formed to beessentially flat with inclined edge portions 71 provided at theirradially inner inlet ends adjacent the cavity 3. In these arrangements,the discs 7 are formed to provide relatively wide fluid entrancepassages 81 in which,' under normal conditions that is when all thediscs 7 are centered relative to each other,

only little pressure drop occurs wherein, however, pressure builds uprapidly wherever the clearance decreases thereby maintaining the discs 7properly centered with respect to each other. The discs are formed toprovide intermediate passage areas 83 which are narrow enough to causeconsiderable pressure drop. At their radially outer ends the discs 7 arethicker so that the width of the exit area 82 in which the rest of thepressure drop occurs is reduced. As shown in FIG. 7, a relatively narrowpath may also be formed at an area 84 adjacent the entrance area 81. Inthe area.84, however, grooves 85 are formed in the discs 7 to insurepressurization of the intermediate ,passage areas 83 when adjacent discsare in contact with each other. In this case, the passagesin the exitareas 82 are somewhat shorter to compensate for the reduced pressure inthe intermediate passage areas 83 as caused by the pressure drop in therelatively narrow area 84.

The disc arrangement shown in FIG. 8 is similar to that of FIG. 7 exceptthat, instead of the grooves 85,

control channels 86 and 87 are provided to insure pressurization of theintermediate'passage areas 83. The control channels 86 providecommunication between the intermediate passage area 83 and the entrancearea 81' or, as shown for the floating ring 12 the control channels 87provide communication between the intermediate passage area 83 and thecavity 3.

As shown in FIGS. 7 to 9 the arrangement may include a floating ring asdescribed for example in this applicants earlier US. Pat. No. 3,619,016.One of the support and load members, for example the load member 1, mayhave a cavity 11 receiving the floating ring 12 which has a land surface61 opposite the land surface 51 of the support member 2. The floatingring 12 is movable in axial direction within the cavity 11 to permitvariation of the leakage passage gaps. A seal 13 is disposed between thefloating ring 12 and the side walls of the cavity 11 to preventuncontrolled leakage of pressurized fluid from the cavity. Preferably,the rear surface 14 of the floating ring 12 which is exposed to the highpressure fluid in the cavity 11 is substantially smaller than the landsurface 61 of the floating ring 12 so that the axial force on thefloating ring 12 as caused by the fluid pressure on the land surface 61is substantially larger than the oppositely directed axial force causedby the high fluid pressure on the rear surface 14 of the floating ring12, the floating ring 12 being maintained in balance by a relativelystrong spring, preferably a Belleville spring.15.

The spring force is a function of the fluid operating pressure and mustincrease very rapidly with only small deflections as the operatingpressure increases, that is, the spring must have a high spring rate.If, for example, in a particular thrust bearing the full load pressureon the floating ring is 1,500 psi with 400 pounds contributed by thespring, the spring rate would typically be 40,000 lb/in. In theparticular bearings shown in the drawings spring rates of at least 5,000lb/inl are considered necessary with a floating ring diameter of about 5inches. The deflection of the spring is very limited, preferably lessthan 0.02 in.

This arrangement is especially advantageous if the load and supportmembers should not make substantial axial movements toward and from eachother. The gap size of the fluid flow passage is then automaticallyadjusted by asking more or less of the spring. The spring alsocompensates in a simple manner for inaccuracies in dimensions, forobstructions by dirt and for variations in the fluid flow volume.

During rotation of the load member relative to the support member,shearing forces occur in the fluid films present in the passages formedbetween the land surfaces. This causes an energy consuming drag whichkeeps the free floating discs moving at speeds between the speeds ofthe. support and load members. The energy consumed depends to a largeextent on the difference of the speed between adjacent surfaces whichdifference is substantially reduced, if, in accordance with the presentinvention, one or more discs are ,floating between the land surfaces.

Assuming, for example, that the support member rests and theload memberrotates at 20,000 rpm, with nineteen discs disposed between the landsurfaces, the speed difference between adjacent surfaces will be only1,000 rpm. Such reduction in the speed difference between adjacentsurfaces is of great advantage since the losses due to shear increasewith the speed difference at a rate equal to a square function of thespeed differ-.

ence.

Also, occasional contact between adjacent surfaces due to vibrationwobble, dirt, or uneven surfaces is of no harm because the relativespeeds are low and the discs are resiliently floating between the landsand, furthermore, have only very small masses.

With the arrangement according to the invention, the combined width ofall flow passages between the lands can be made substantially largerthan the width of a single passage with equal fluid pressures and fluidflows.

With N passages provided between the lands, the total gap flow width ofthe N fluid flow passages between the lands is N two-thirds times thewidth and the shear losses are l/N five-thirds times that of a singlegap flow path with equal fluid pressure and fluid flow. For example,with N=5, the total width of the five passages forming the path betweenthe lands is 2.9 times the width of a single gap path and the shearlosses are only l/l4.6 or only 7 percent of those obtained for a bearingwith a single gap fluid flow path.

The invention is, of course, not restricted to the arrangements shown inthe embodiments as described. The annular discs disposed between thelands may be flat, for example, especially if the bearing structure isnot intended to accommodate any radial forces. It is, however, necessaryto have some provision causing separation of the discs in the bearingstructure to form the various fluid flow passages. Separation of flatdiscs may be insured, for example, by a reduction of the thickness ofthe discs at the entrance end of the fluid flow path or by radialgrooves which permit the pressurized fluid to enter the passages betweenadjacent discs for separation thereof.

Also, as shown in FIG. 9, areas of the same pressure between the discsmaybe in communication with each other by passages 88 extending betweenannular grooves 89 formed in the faces of the discs. Furthermore, asalso indicated in FIG. 9, seals 16 and 17 may be provided at theradially inner and outer ends of the Belleville spring 15, no sealsbeing provided between the floating ring 12 and the side walls of thecavity 11 so that the Belleville spring 15 is exposed only at one sideto the high pressure fluid in the cavity 11. Further, the Bellevillespring 15 may be integral with or firmly connected to, the floating ring12 as by welding so that seal 16 is not necessary. Also, the Bellevilletype spring may consist ofa circular plate to eliminate the need for anyseal.

What we claim is:

1. In a hydrostatic thrust bearing including: a support member; arotatable load member disposed adjacent said support member, saidmembers having a cavity formed therebetween; and means for admitting apressurized fluid to said cavity for supporting said load member on saidsupport member, said members having opposite lands extending around saidcavity and forming a leakage path for the fluid admitted to said cavity,the improvement comprising: at least one annular disc disposed betweensaid opposite lands and dividing said leakage path into at least twoparallel passages, each disc being freely rotatable in said leakage pathto pro vide, during rotation of said load member, smaller relativespeeds between adjacent surfaces of said parallel passages than betweensaid support and load members.

2. A bearing as claimed in claim 1, wherein the lands and discs arespaced from each other at the entrance end of said leakage path therebyto ensure separation of the discs when fluid passesthrough the leakagepath.

3. A bearing as claimed in claim 2, wherein each disc is of uniformthickness but the land surfaces and each disc disposed therebetween arecurved in the form of a dish having essentially radial inlet areasthereby providing a space between adjacent discs at the radially innerentrance end of the leakage path.

4. A bearing as claimed in claim 2, wherein the discs are of reducedthickness at their radially inner ends.

5. A bearing as claimed in claim 3, wherein said discs are of reducedthickness at their radially outer end to provide diverging exit areasfor said fluid passages.

6. A bearing as claimed in claim 1, wherein each disc is composed of tworings having different curvatures and engaging each other only at theirradially inner and outer ends, thereby providing passages of increasedwidth at the entrance and exit ends of said leakage paths.

7. A bearing as claimed in claim 1, wherein the land surfaces and thediscstherebetween are dish-shaped providing essentially axial inlet andoutlet fluid passage areas and intermediate areas which are inclinedwith respect to the inlet and outlet areas, the discs being of uniformthickness.

8. A bearing as claimed in claim 1, wherein said discs are essentiallyflat but have inclined radially inner end portions.

9. A bearing as claimed in claim 8, wherein said discs are formed toprovide narrower exit passage areas than inlet passage areas.

10. A bearing as claimed in claim 8, wherein there are provided adjacentthe inclined inner end portions annular passage areas which haveessentially the same width as the exit areas, said discs having radialgrooves formed therein in said annular passage areas to insurepressurization of all the passages and separation of all discs.

11. A bearing as claimed in claim 8, wherein there are provided adjacentthe inclined inner end portions annular passage areas which haveessentially the same width as the exit areas with an intermediatepassage area of greater width between the inlet and exit areas andwherein control channels are provided bypassing the annular passageareas adjacent the inclined inner end portions to insure pressurizationof said intermediate passage area. I

12. A bearing as claimed in claim 1, wherein one of said lands isassociated with a floating ring axially movably disposed in apressurized fluid filled cavity formed in one of said load and supportmembers, the rear surface of the floating ring which is exposed to thepressurized fluid being substantially smaller than its land surface sothat the axial force caused by the fluid pressure on the land surface issubstantially larger than the oppositely directed axial force caused bythe fluid pressure on said rear surface and a spring with high springrate is effective on said floating ring to maintain the floating ring inbalance.

13. A bearing as claimedin claim 12, wherein said spring is a Bellevillespring disposed between the floating ring and cavity end wall.

14. A bearing as claimed in claim 12, wherein said ring has a springrate high enough to permit a total spring deflection of less than 0.02inches.

15. A bearing as claimed in claim 1, wherein areas of the same pressurein said parallel passage are in communication with each other bycommunication passages formed in said discs.

16. [n a hydrostatic bearing including: a support member; a rotatableload member disposed adjacent said support member, one of said membershaving a cavity formed therein adjacent the other member; means foradmitting pressurized fluid to said cavity; and a floating ring axiallymovably disposed in said cav- 8 circular spring is an annular Bellevilletype spring having sealing means disposed at its contact areas with thefloating ring and the cavity walls.

18. A hearing as claimed in claim 16, wherein said circular spring is adisc made integral with the floating ring.

1. In a hydrostatic thrust bearing including: a support member; arotatable load member disposed adjacent said support member, saidmembers having a cavity formed therebetween; and means for admitting apressurized fluid to said cavity for supporting said load member on saidsupport member, said members having opposite lands extending around saidcavity and forming a leakage path for the fluid admitted to said cavity,the improvement comprising: at least one annular disc disposed betweensaid opposite lands and dividing said leakage path into at least twoparallel passages, each disc being freely rotatable in said leakage pathto provide, during rotation of said load member, smaller relative speedsbetween adjacent surfaces of said parallel passages than between saidsupport and load members.
 2. A bearing as claimed in claim 1, whereinthe lands and discs are spaced from each other at the entrance end ofsaid leakage path thereby to ensure separation of the discs when fluidpasses through the leakage path.
 3. A bearing as claimed in claim 2,wherein each disc is of uniform thickness but the land surfaces and eachdisc disposed therebetween are curved in the form of a dish havingessentially radial inlet areas thereby providing a space betweenadjacent discs at the radially inner entrance end of the leakage path.4. A bearing as claimed in claim 2, wherein the discs are of reducedthickness at their radially inner ends.
 5. A bearing as claimed in claim3, wherein said discs are of reduced thickness at their radially outerend to provide diverging exit areas for said fluid passages.
 6. Abearing as claimed in claim 1, wherein each disc is composed of tworings having different curvatures and engaging each other only at theirradially inner and outer ends, thereby providing passages of increasedwidth at the entrance and exit ends of said leakage paths.
 7. A bearingas claimed in claim 1, wherein the land surfaces and the discstherebetween are dish-shaped providing essentially axial inlet andoutlet fluid passage areas and intermediate areas which are inclinedwith respect to the inlet and outlet areas, the discs being of uniformthickness.
 8. A bearing as claimed in claim 1, wherein said discs areessentially flat but have inclined radially inner end portions.
 9. Abearing as claimed in claim 8, wherein said discs are formed to providenarrower exit passage areas than inlet passage areas.
 10. A bearing asclaimed in claim 8, wherein there are provided adjacent the inclinedinner end portions annular passage areas which have essentially the samewidth as the exit areas, said discs having radial grooves formed thereinin said annular passage areas to insure pressurization of all thepassages and separation of all discs.
 11. A bearing as claimed in claim8, wherein there are provided adjacent the inclined inner end portionsannular passage areas which have essentially the same width as the exitareas with an intermediate passage area of greater width between theinlet and exit areas and wherein control channels are provided bypassingthe annular passage areas adjacent the inclined inner end portions toinsure pressurization of said intermediate passage area.
 12. A bearingas claimed in claim 1, wherein one of said lands is associated with afloating ring axially movably disposed in a pressurized fluid filledcavity formed in one of said load and suppoRt members, the rear surfaceof the floating ring which is exposed to the pressurized fluid beingsubstantially smaller than its land surface so that the axial forcecaused by the fluid pressure on the land surface is substantially largerthan the oppositely directed axial force caused by the fluid pressure onsaid rear surface and a spring with high spring rate is effective onsaid floating ring to maintain the floating ring in balance.
 13. Abearing as claimed in claim 12, wherein said spring is a Bellevillespring disposed between the floating ring and cavity end wall.
 14. Abearing as claimed in claim 12, wherein said ring has a spring rate highenough to permit a total spring deflection of less than 0.02 inches. 15.A bearing as claimed in claim 1, wherein areas of the same pressure insaid parallel passage are in communication with each other bycommunication passages formed in said discs.
 16. In a hydrostaticbearing including: a support member; a rotatable load member disposedadjacent said support member, one of said members having a cavity formedtherein adjacent the other member; means for admitting pressurized fluidto said cavity; and a floating ring axially movably disposed in saidcavity, said floating ring and said other member having opposite landsurfaces to provide a controlled fluid leakage path therebetween; theimprovement comprising a circular spring disposed between said floatingring and said one member and sealingly engaging at its outer end saidfloating ring and abutting the walls of said cavity to preventuncontrolled fluid leakage therefrom.
 17. A bearing as claimed in claim16, wherein said circular spring is an annular Belleville type springhaving sealing means disposed at its contact areas with the floatingring and the cavity walls.
 18. A bearing as claimed in claim 16, whereinsaid circular spring is a disc made integral with the floating ring.